In response to the ten "best" list, here is my list of the ten most "important" acoustic guitars.

#10. Ovation Balladeer. I'm not a big fan of Ovations but they did introduce the whole idea of acoustics made of something other than wood.
#9 Guild Jumbo 12. F-212/412/512. At least for me what a Jumbo 12 should sound like.
#8 Washburn Festival. Seems normal now but in the mid 80's the thin body acoustic electric was pretty revolutionary. Bettencourt's finger picking on "More than Words" made the idea popular.
#7 Gibson L-1. Most often associated with Robert Johnson. The small blues box.
#6 Epiphone Texan FT-79. McCartney used it to record Yesterday.
#5 Harmony Sovereign H1260. A poor mans D-18 but Page put it to good use on the intro to "Stairway to Heaven".
#4 Martin Om/000-28. Going to 14 frets clear with a solid headstock made the "Orchestra Model" the first modern flat top.
#3 Gibson J-200 King of the Flattops.
#2 Martin/Ditson Dreadnought. 1916, the first "dread". Out of that came the D-18 and D-28.
#1 Martin D-45.